Field
Embodiments of the present invention generally relate to conditioning a polishing pad for polishing a substrate, such as a semiconductor wafer.
Description of the Related Art
In the fabrication of integrated circuits and other electronic devices on substrates, multiple layers of conductive, semiconductive, and dielectric materials are deposited on or removed from a feature side, i.e., a deposit receiving surface, of a substrate. As layers of materials are sequentially deposited and removed, the feature side of the substrate may become non-planar and require planarization and/or polishing. Planarization and polishing are procedures where previously deposited material is removed from the feature side of the substrate to form a generally even, planar or level surface. The procedures are useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, and scratches. The procedures are also useful in forming features on a substrate by removing excess deposited material used to fill the features and to provide an even or level surface for subsequent deposition and processing.
During polishing processes, the polishing surface of the pad that is in contact with the feature side of the substrate experiences a deformation. The deformation includes smoothing of the polishing surface and/or unevenness in the plane of the polishing surface, as well as clogging or blockage of pores in the polishing surface that may lessen the ability of the pad to properly and efficiently remove material from the substrate. Periodic conditioning of the polishing surface is required to maintain a consistent roughness, porosity and/or a generally flat profile across the polishing surface.
One method to condition the polishing surface utilizes an abrasive conditioning disk that is urged against the polishing surface while being rotated and/or swept across the majority of the polishing surface. The abrasive portion of the conditioning disk, which may be diamond particles or other hard materials, typically cut into the pad surface, which forms grooves in, and otherwise roughens, the polishing surface. However, while the rotation and/or downforce applied to the conditioning disk is controlled, the abrasive portion may not cut into the polishing surface evenly, which creates a difference in roughness across the polishing surface. Fluid jet systems have been utilized to condition the polishing pad in lieu of abrasive disks, but these systems use great amounts of fluid and are expensive to operate. Other systems utilizing optical devices (e.g., lasers) that cut into the polishing surface have also been utilized. However, the optical energy interacts with polishing fluids on the pad, causing boiling of the fluid which may rupture pores in the polishing surface. With each of the aforementioned conditioning regimes, roughness across the polishing surface is not adequately controllable such that the roughness across the polishing surface is non-uniform. Additionally, as the cutting action is not readily controlled, the pad lifetime may be shortened. Further, the cutting action of these conditioning devices and systems sometimes produce large asperities in the polishing surface. While the asperities are beneficial in the polishing process, the asperities may break loose during polishing, which creates debris that may contribute to defects in the substrate.
Therefore, there is a need for a method and apparatus that facilitates uniform conditioning of the polishing surface of a polishing pad.